Polymeric laminates may be used for the storage of agricultural products and the like, such as harvested grain, silage.
In agricultural production, it is beneficial to prevent post-harvest loss through the use of on-farm storage techniques and containers.
There are several concomitant problems attendant to on-farm storage of dry foodstuffs (e.g., grain and feedstock), such as the prevention of water ingress and the subsequent moisture accumulation in the surface layer of the grain adjacent the innermost layer of the container.
Free-standing storage containers for bagged agricultural commodities are prone to insect infestation and infestation development and growth of molds and resulting toxins. In addition, long term storage of dry foodstuffs typically is threatened by rodents and insects, as well as by bacteria fungus, such as aflatoxin. Accordingly, it is beneficial to provide on-farm storage containers that prevent or reduce the infestation and fungal growth. To reduce fungal growth, the containers should maintain some degree of oxygen permeability.
The container must also have sufficient strength and resiliency to withstand the forces associated with grain storage and transport.
In the preparation of polymeric materials of this type for these purposes, there has been a deficiency in the prior art in that, while the prevention of water ingress and associated moisture accumulation, as well as the use of rodent repellants, insecticides and fungicides are known, prior structural materials have not been able to achieve effective oxygen transmission (i.e., reduce oxygen flow toward the foodstuff and allow oxygen to flow away from the foodstuff), water vapor transmission and moisture management (i.e., water absorbancy) so as to be able to effectively reduce the risks associated with fungal growth, aflatoxin and mycotoxins; all while providing the other benefits of the active ingredients above.
Post-harvest losses due to poor handling, poor storage, insect infestations and mold or rot significantly hinder income generation for small-scale farmers. “In Tanzania, maize losses of up to 35% may occur due to Prostephanus truncatus (Larger Grain Borer) within 5 to 6 months if improperly stored (Mallya, 1992) and up to 60% losses may occur after 9 months of storage (Keil, 1988), a situation which may result in serious famine” according to the FAO's Paper on Insect Damage, Post Harvest Compendium. In Kenyan highlands, total losses due to pests in maize were estimated at 57% with insects being more important than disease (Grisley, 1997). In Zimbabwe, grain damage of 92% in stored maize was reported due to insect pests, treatment with malthion reduced damage by only 10% (Matrio, et al. 1992). Infestations of stored cowpeas can be as high as 90% in markets and in village stores (Alabeek, 1996). A wide variety of food stuffs are affected by insects, mold and fungi infestation is not limited to maize grains and pulses. Insect pests, in addition to fungal diseases, are responsible for 50% damage in cassava (Maninek, 1994). Losses of up to 70% in dried cassava roots after 4 months of storage were reportedly due to P. truncatus. (Hodges, et al., 1985).
Insect pests inflict their damage on stored products mainly by direct feeding. Some species feed on the endosperm, causing loss of weight and quality, while other species feed on the germ, resulting in poor seed germination and less viability (Malek & Parveen, 1989; Santus, et al. 1990). In addition to direct consumption of the product, insect pests contaminate their feeding media through excretion, molting, dead bodies and their own existence in the product which is not commercially desirable. Damage done by insect pests encourages infection with bacteria and fungal disease through transmission of their spores (Cravedi & Quaroni, 1982; E. Kundayo, 1988; Dunkel, 1980). The presence of insects also raises the stored product temperature, due to their feeding activity, resulting in hot spots (Appert, 1987; Mills, 1989). These “hot spots” can lead to condensation and excessive moisture, resulting in the growth of mold or fungi. Insects activity can have a profound effect on the spread of fungal diseases through transmitting the spores and increasing the surface area susceptible to fungal infection, which eventually increases production of mycotoxins (Dunkel, 1988).
Despite the physical damage of insect pests, infestations resulting from poor post-harvest storage can have economically devastating effects on farmers, communities, and the economies of several countries depending on exportation of maize, wheat and other food stuffs. For example, P. truncatus cost Tanzania roughly US $91 million annually in lost maize intended for consumption or export (Bionet International & Global Invasion Species Program). Farmers in sub-Sharan Africa are frequently forced to sell stored produce prematurely because of the deterioration due to insect damage that occurs if storage periods are extended (Global, et al. 1996, Brice et al. 1996, Marsland & Golob 1996, Donaldson, et al., 1996). Inability to store and protect post-harvest leads to significant income loss as farmers do not have the flexibility to wait for the higher price as the market fluctuates. The difficulties of on-farm food storage and the economic burden of post-harvest loss are devastating for farmers in developing countries, particularly due to the lack of available resources for building of storage units, the lack of information regarding insecticide/pesticide use, as well as lack of affordability.
On-farm storage difficulties and post-harvest losses occur mainly as a result of temperature, moisture, respiration of stored contents, infestation of insects, infestation of rodents and fumonisins, mycotxins and aflatoxins resulting from mold and fungi growth, due to lack of oxygen transmission and water vapor transmission of storage containers presently employed. Whether intended for human consumption, or used as animal food stock, stored product contamination poses serious health risks. Aflatoxin consumed by dairy cattle, though altered in their body, still remains toxic and shows up in the milk (Christensen & Meronuck, 1986, Gwinner, et al., 1996). A. fumagatis is report to result in high levels of abortion in cattle feeding on contaminated food; also infects human lungs (Darwish, et al., 1991; Pandey & Prasad 1993; Abud, et al., 1995).
The use of plastic sacks, bag storage, prefabricated iron halls and flexible plastic silos are increasingly gaining ground among farmers for short term storage (Peterson & Simila, 1990; Compton, et al., 1993; Bartali, 1994). However, none of the current storage mechanisms effectively manage the comprehensive set of factors including insect and pest repellency, barrier to oxygen, etc.
Accordingly, there remains a need for improved polymeric and woven laminates for dry on-farm storage of dry foodstuffs.